The microwave oven as the representative microwave heating apparatus can heat directly the foods as the representative subject to be heated. Therefore, its convenience of needing no cooking pan or pot makes the microwave oven the apparatus indispensable to life. Up to now, the microwave oven having a food loading space, width and depth dimensions of which is about 300 to 400 mm respectively and a height dimension of which is about 200 mm, of the heating chamber through which a microwave propagates is widespread commonly.
In recent years, the products having a laterally wide heating chamber whose food loading space has a flat bottom surface and whose lateral width is widened by setting the width dimension to 400 mm or more relatively larger than the depth dimension such that a plurality of foods can be heated in parallel to enhance its convenience are put to practical use.
Also, on account of the progress of functionality of the microwave oven, the microwave oven equipped with a “grill menu” as well as a so-called “hot-up menu” (a high-frequency heating that heats a food by radiating a microwave to the food) which is traditionally provided is put onto the market. The “grill menu” means a cooking menu to cook the food in a grilling fashion (in which a food is cooked so as to have a crispy surface and a juicy inside) by a method to heat a food via a heating pan by raising a temperature of the heating pan on which the food is put, a method to heat the food by a grilling heater, or their combination.
Traditionally, as shown in FIG. 17, this type of a high-frequency heating apparatus 300 includes a waveguide 303 for propagating a microwave radiated from a magnetron 302 as a representative microwave generating means, a heating chamber 301, a loading table 306 fixed in the heating chamber 301 into which a food (not shown) as a representative subject to be heated is put and made of the low-loss dielectric material such as ceramic, glass, or the like to transmit the microwave easily, an antenna space 310 formed below the loading table 306 in the heating chamber 301, a rotation antenna 305 fitted to the center of the heating chamber 301 from the waveguide 303 to the antenna space 310 to radiate the microwave propagated through the waveguide 303 to the interior of the heating chamber 301, a motor 304 as a representative driving means for turning/driving the rotation antenna 305, a heating plate 308 provided in the heating chamber 301 according to the application, a plate bearing portion 307 for supporting the heating plate 308, and a heater 309 for performing the electric heating.
In the hot-up menu that heats directly the subject to be heated by the high-frequency heating, the high-frequency heating is executed in a situation that the food, or the like is put on the loading table 306. The microwave being radiated from the magnetron 302 is absorbed once by the rotation antenna 305 via the waveguide 303, and then this microwave is radiated toward the heating chamber 301 from an upper surface of the radiation portion of the rotation antenna 305. At this time, in order to stir the microwave uniformly in the heating chamber 301, normally the rotation antenna 305 radiates the microwave while turning at a predetermined speed.
Also, when the grill menu to cook the food in a grilling fashion is chosen, the food (e.g., dark meat, fish, or the like) is put on the heating plate 308 that is supported by the plate bearing portion 307. In this state, a surface portion of the food is heated/processed by the heater 309 positioned on the upper side of the food. Also, a back surface portion of the food is heated/processed by the heating plate 308 whose temperature is raised by the microwave.
In the heating cooking that concentrates the microwave onto the food, moisture contained in the inside of the food is evaporated excessively because of the property of microwave. In contrast, the process of heating the food by both the heater and the heating plate can finish the food in the so-called grilling fashion to finish a surface of the food crisply while confining a moisture or a taste in the inside of the food (see Patent Literature 1).
Patent Literature 1: JP-A-2004-071216